Fix user-change handling for colliders as well as disabled colliders (#900)

* feat: add debug-demo for disabling a collider

* feat: add a simple debug-demo with two cubes

* feat: rename RigidBodyChangnes::MODIFIED and ColliderChanges::MODIFIED to ::IN_MODIFIED_SET

* feat: render debug-colliders with a different color with the debug-renderer

* chore: wire up new examples to the testbed

* fix colliders user-modification being ignored after the first step

* fix broad-phase still taking into account disabled colliders with enabled dynamic rigid-bodies

* chore: update changelog

* fix cargo doc

CHANGELOG.md

@@ -1,10 +1,18 @@
 ## Unreleased
 
-- `InteractionGroups` struct now contains `InteractionTestMode`. Continues [rapier/pull/170](https://github.com/dimforge/rapier/pull/170) for [rapier/issues/622](https://github.com/dimforge/rapier/issues/622)
-- `InteractionGroups` constructor now requires an `InteractionTestMode` parameter. If you want same behaviour as before, use `InteractionTestMode::And` (eg. `InteractionGroups::new(Group::GROUP_1, Group::GROUP_1, InteractionTestMode::And)`)
+- `InteractionGroups` struct now contains `InteractionTestMode`.
+  Continues [rapier/pull/170](https://github.com/dimforge/rapier/pull/170)
+  for [rapier/issues/622](https://github.com/dimforge/rapier/issues/622)
+- `InteractionGroups` constructor now requires an `InteractionTestMode` parameter. If you want same behaviour as before,
+  use `InteractionTestMode::And` (eg.
+  `InteractionGroups::new(Group::GROUP_1, Group::GROUP_1, InteractionTestMode::And)`)
 - `CoefficientCombineRule::Min` - now makes sure it uses a non zero value as result by using `coeff1.min(coeff2).abs()`
 - `InteractionTestMode`: Specifies which method should be used to test interactions. Supports `AND` and `OR`.
 - `CoefficientCombineRule::ClampedSum` - Adds the two coefficients and does a clamp to have at most 1.
+- Rename `ColliderChanges::CHANGED` to `::IN_CHANGED_SET` to make its meaning more precise.
+- Rename `RigidBodyChanges::CHANGED` to `::IN_CHANGED_SET` to make its meaning more precise.
+- Fix colliders ignoring user-changes after the first simulation step.
+- Fix broad-phase incorrectly taking into account disabled colliders attached to an enabled dynamic rigid-body.
 
 ## v0.30.1 (17 Oct. 2025)
 

examples3d/all_examples3.rs

@@ -41,10 +41,12 @@ mod joints3;
 mod character_controller3;
 mod debug_chain_high_mass_ratio3;
 mod debug_cube_high_mass_ratio3;
+mod debug_disabled3;
 mod debug_internal_edges3;
 mod debug_long_chain3;
 mod debug_multibody_ang_motor_pos3;
 mod debug_sleeping_kinematic3;
+mod debug_two_cubes3;
 mod gyroscopic3;
 mod inverse_kinematics3;
 mod joint_motor_position3;
@@ -106,6 +108,8 @@ pub fn main() {
         ("(Debug) big colliders", debug_big_colliders3::init_world),
         ("(Debug) boxes", debug_boxes3::init_world),
         ("(Debug) balls", debug_balls3::init_world),
+        ("(Debug) disabled", debug_disabled3::init_world),
+        ("(Debug) two cubes", debug_two_cubes3::init_world),
         ("(Debug) pop", debug_pop3::init_world),
         (
             "(Debug) dyn. coll. add",

examples3d/debug_disabled3.rs

@@ -0,0 +1,59 @@
+use rapier_testbed3d::Testbed;
+use rapier3d::prelude::*;
+
+pub fn init_world(testbed: &mut Testbed) {
+    let mut bodies = RigidBodySet::new();
+    let mut colliders = ColliderSet::new();
+    let impulse_joints = ImpulseJointSet::new();
+    let multibody_joints = MultibodyJointSet::new();
+
+    let rad = 0.5;
+
+    /*
+     * Ground
+     */
+    let ground_size = 10.1;
+    let ground_height = 2.1;
+
+    let rigid_body = RigidBodyBuilder::fixed().translation(vector![0.0, -ground_height, 0.0]);
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(ground_size, ground_height, ground_size);
+    colliders.insert_with_parent(collider, handle, &mut bodies);
+
+    /*
+     * Platform that will be enabled/disabled.
+     */
+    let rigid_body = RigidBodyBuilder::dynamic().translation(vector![0.0, 5.0, 0.0]);
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(5.0, 1.0, 5.0);
+    let handle_to_disable = colliders.insert_with_parent(collider, handle, &mut bodies);
+
+    // Callback that will be executed on the main loop to handle proximities.
+    testbed.add_callback(move |mut graphics, physics, _, run_state| {
+        if run_state.timestep_id % 250 == 0 {
+            let co = &mut physics.colliders[handle_to_disable];
+            let enabled = co.is_enabled();
+            co.set_enabled(!enabled);
+            println!("Platform is now enabled: {}", co.is_enabled());
+        }
+
+        if run_state.timestep_id % 25 == 0 {
+            let rigid_body = RigidBodyBuilder::dynamic().translation(vector![0.0, 20.0, 0.0]);
+            let handle = physics.bodies.insert(rigid_body);
+            let collider = ColliderBuilder::cuboid(rad, rad, rad);
+            physics
+                .colliders
+                .insert_with_parent(collider, handle, &mut physics.bodies);
+
+            if let Some(graphics) = &mut graphics {
+                graphics.add_body(handle, &physics.bodies, &physics.colliders);
+            }
+        }
+    });
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world(bodies, colliders, impulse_joints, multibody_joints);
+    testbed.look_at(point![-30.0, 4.0, -30.0], point![0.0, 1.0, 0.0]);
+}

examples3d/debug_two_cubes3.rs

@@ -0,0 +1,29 @@
+use rapier_testbed3d::Testbed;
+use rapier3d::prelude::*;
+
+pub fn init_world(testbed: &mut Testbed) {
+    /*
+     * World
+     */
+    let mut bodies = RigidBodySet::new();
+    let mut colliders = ColliderSet::new();
+    let impulse_joints = ImpulseJointSet::new();
+    let multibody_joints = MultibodyJointSet::new();
+
+    // Dynamic box rigid body.
+    let rigid_body = RigidBodyBuilder::dynamic().translation(vector![0.0, 2.0, 0.0]);
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(0.5, 0.5, 0.5);
+    colliders.insert_with_parent(collider, handle, &mut bodies);
+
+    let rigid_body = RigidBodyBuilder::fixed();
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(0.5, 0.5, 0.5);
+    colliders.insert_with_parent(collider, handle, &mut bodies);
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world(bodies, colliders, impulse_joints, multibody_joints);
+    testbed.look_at(point![10.0, 10.0, 10.0], Point::origin());
+}

src/dynamics/rigid_body_components.rs

@@ -111,8 +111,8 @@ bitflags::bitflags! {
     #[derive(Copy, Clone, PartialEq, Eq, Debug)]
     /// Flags describing how the rigid-body has been modified by the user.
     pub struct RigidBodyChanges: u32 {
-        /// Flag indicating that any component of this rigid-body has been modified.
-        const MODIFIED    = 1 << 0;
+        /// Flag indicating that this rigid-body is in the modified rigid-body set.
+        const IN_MODIFIED_SET = 1 << 0;
         /// Flag indicating that the `RigidBodyPosition` component of this rigid-body has been modified.
         const POSITION    = 1 << 1;
         /// Flag indicating that the `RigidBodyActivation` component of this rigid-body has been modified.
@@ -1061,10 +1061,7 @@ impl RigidBodyColliders {
         co_handle: ColliderHandle,
     ) {
         if let Some(i) = self.0.iter().position(|e| *e == co_handle) {
-            rb_changes.set(
-                RigidBodyChanges::MODIFIED | RigidBodyChanges::COLLIDERS,
-                true,
-            );
+            rb_changes.set(RigidBodyChanges::COLLIDERS, true);
             self.0.swap_remove(i);
         }
     }
@@ -1083,10 +1080,7 @@ impl RigidBodyColliders {
         co_shape: &ColliderShape,
         co_mprops: &ColliderMassProps,
     ) {
-        rb_changes.set(
-            RigidBodyChanges::MODIFIED | RigidBodyChanges::COLLIDERS,
-            true,
-        );
+        rb_changes.set(RigidBodyChanges::COLLIDERS, true);
 
         co_pos.0 = rb_pos.position * co_parent.pos_wrt_parent;
         rb_ccd.ccd_thickness = rb_ccd.ccd_thickness.min(co_shape.ccd_thickness());
@@ -1113,6 +1107,8 @@ impl RigidBodyColliders {
     ) {
         for handle in &self.0 {
             // NOTE: the ColliderParent component must exist if we enter this method.
+            // NOTE: currently, we are propagating the position even if the collider is disabled.
+            //       Is that the best behavior?
             let co = colliders.index_mut_internal(*handle);
             let new_pos = parent_pos * co.parent.as_ref().unwrap().pos_wrt_parent;
 

src/dynamics/rigid_body_set.rs

@@ -31,12 +31,12 @@ pub(crate) type ModifiedRigidBodies = ModifiedObjects<RigidBodyHandle, RigidBody
 impl HasModifiedFlag for RigidBody {
     #[inline]
     fn has_modified_flag(&self) -> bool {
-        self.changes.contains(RigidBodyChanges::MODIFIED)
+        self.changes.contains(RigidBodyChanges::IN_MODIFIED_SET)
     }
 
     #[inline]
     fn set_modified_flag(&mut self) {
-        self.changes |= RigidBodyChanges::MODIFIED;
+        self.changes |= RigidBodyChanges::IN_MODIFIED_SET;
     }
 }
 

src/geometry/broad_phase_bvh.rs

@@ -69,10 +69,6 @@ impl BroadPhaseBvh {
     /// sent previously and no `RemovePair` happened since then). Sending redundant events is allowed
     /// but can result in a slight computational overhead.
     ///
-    /// The `colliders` set is mutable only to provide access to
-    /// [`collider.set_internal_broad_phase_proxy_index`]. Other properties of the collider should
-    /// **not** be modified during the broad-phase update.
-    ///
     /// # Parameters
     /// - `params`: the integration parameters governing the simulation.
     /// - `colliders`: the set of colliders. Change detection with `collider.needs_broad_phase_update()`

src/geometry/collider_components.rs

@@ -35,8 +35,8 @@ bitflags::bitflags! {
     #[derive(Copy, Clone, PartialEq, Eq, Debug)]
     /// Flags describing how the collider has been modified by the user.
     pub struct ColliderChanges: u32 {
-        /// Flag indicating that any component of the collider has been modified.
-        const MODIFIED = 1 << 0;
+        /// Flag indicating that the collider handle is in the changed collider set.
+        const IN_MODIFIED_SET = 1 << 0;
         /// Flag indicating that the density or mass-properties of this collider was changed.
         const LOCAL_MASS_PROPERTIES = 1 << 1; // => RigidBody local mass-properties update.
         /// Flag indicating that the `ColliderParent` component of the collider has been modified.

src/geometry/collider_set.rs

@@ -11,12 +11,12 @@ pub type ModifiedColliders = ModifiedObjects<ColliderHandle, Collider>;
 impl HasModifiedFlag for Collider {
     #[inline]
     fn has_modified_flag(&self) -> bool {
-        self.changes.contains(ColliderChanges::MODIFIED)
+        self.changes.contains(ColliderChanges::IN_MODIFIED_SET)
     }
 
     #[inline]
     fn set_modified_flag(&mut self) {
-        self.changes |= ColliderChanges::MODIFIED;
+        self.changes |= ColliderChanges::IN_MODIFIED_SET;
     }
 }
 

src/pipeline/debug_render_pipeline/debug_render_pipeline.rs

@@ -327,6 +327,8 @@ impl DebugRenderPipeline {
                             c[2] * coeff[2],
                             c[3] * coeff[3],
                         ]
+                    } else if !co.is_enabled() {
+                        self.style.disabled_color_multiplier
                     } else {
                         self.style.collider_parentless_color
                     };

src/pipeline/physics_pipeline.rs

@@ -82,6 +82,12 @@ impl PhysicsPipeline {
         colliders: &mut ColliderSet,
         modified_colliders: &mut ModifiedColliders,
     ) {
+        // TODO: we can’t just iterate on `modified_colliders` here to clear the
+        //       flags because the last substep will leave some colliders with
+        //       changes flags set after solving, but without the collider being
+        //       part of the `ModifiedColliders` set. This is a bit error-prone but
+        //       is necessary for the modified information to carry on to the
+        //       next frame’s narrow-phase for updating.
         for co in colliders.colliders.iter_mut() {
             co.1.changes = ColliderChanges::empty();
         }
@@ -700,12 +706,32 @@ impl PhysicsPipeline {
                 // If we ran the last substep, just update the broad-phase bvh instead
                 // of a full collision-detection step.
                 for handle in modified_colliders.iter() {
-                    let co = &colliders[*handle];
+                    let co = colliders.index_mut_internal(*handle);
+                    // NOTE: `advance_to_final_positions` might have added disabled colliders to
+                    //       `modified_colliders`. This raises the question: do we want
+                    //       rigid-body transform propagation to happen on disabled colliders if
+                    //       their parent rigid-body is enabled? For now, we are propagating as
+                    //       it feels less surprising to the user and makes handling collider
+                    //       re-enable less awkward.
+                    if co.is_enabled() {
                         let aabb = co.compute_broad_phase_aabb(&integration_parameters, bodies);
                         broad_phase.set_aabb(&integration_parameters, *handle, aabb);
                     }
+
+                    // Clear the modified collider set, but keep the other collider changes flags.
+                    // This is needed so that the narrow-phase at the next timestep knows it must
+                    // not skip these colliders for its update.
+                    // TODO: this doesn’t feel very clean, but leaving the collider in the modified
+                    //       set would be expensive as this will be traversed by all the user-changes
+                    //       functions. An alternative would be to maintain a second modified set,
+                    //       one for user changes, and one for changes applied by the solver but that
+                    //       feels a bit too much. Let’s keep it simple for now and we’ll see how it
+                    //       goes after the persistent island rework.
+                    co.changes.remove(ColliderChanges::IN_MODIFIED_SET);
+                }
+
+                // Empty the modified colliders set. See comment for `co.change.remove(..)` above.
                 modified_colliders.clear();
-                // self.clear_modified_colliders(colliders, &mut modified_colliders);
             }
         }